A new communications tool that "whispers" on busy radio channels could enable broadband Internet services for on-the-go wireless devices or hook up homes that cannot yet get fast Web access, its inventor said.

xMax, the latest innovation in broadband communications, is a very quiet radio system that uses radio channels already filled up with noisy pager or TV signals, said inventor Joe Bobier.

"xMax is trespassing radio frequencies, although trespassing is not the right word, because we're allowed to transmit a signal if it doesn't interfere with other, stronger signals," said Bobier.

What is unique about the system is that it can emit signals that are too weak to be picked up by normal antennas, but that can be "heard" by special aerials which know where to "listen," thus enabling dual usage of the same scarce radio spectrum.

The technology could interest a telecoms or Internet operator with no radio spectrum because it can begin a wireless broadband service with very few base stations and add more stations and increase density as demand rises.

It is also appealing for rural areas which operators find too costly to cover with the current third-generation mobile phone networks which need base stations every few miles.

"We're talking about a 400 to 500 percent improvement in range," Bobier said, adding that this was still much better than Flash-OFDM, also touted as a rural area broadband system.

XG Technology, the Florida-based company which owns xMax, is in discussions with several chipmakers and equipment makers to build the hardware.

Radio chips for devices should be in the $5 to $6 range when built in volume while base stations will be around $350,000. Those prices are competitive considering the range covered.

The power to penetrateStuart Schwartz, an electrical engineering professor at Princeton University, said xMax is not an efficient system to transport data through the airwaves, "but it is doing it in a benign way. You won't even know it's there. It's very clever."

The advantage is not only that radio spectrum can be used twice and that xMax needs no special radio band of its own, but especially that it can sit in the valuable low-frequency bands which characteristically carry very far and through buildings.

Other new broadband Internet technologies, such as WiMax and Flash OFDM, need dedicated radio frequency bands. If they are situated in frequency ranges above 1GHz, the signal has trouble penetrating buildings and other obstacles, or traveling over distances longer than a few miles.

"We offer long range as well as high speed," Bobier said.

The radio technology can also be used in higher frequencies, and even in wired systems, but the company aims at low-frequency wireless networks first.

"The sweet spot for xMax happens to be in the lower frequencies," said Rick Mooers, executive chairman of XG Technology.

Bobier found a way to put one bit of data on one radio frequency cycle and recover that weak signal with a newly invented filter. If xMax uses a powerful carrier signal--which does require a dedicated, albeit very narrow radio band--it can even extend its range and capacity.

The first xMax network is currently being built in Miami and Fort Lauderdale where one base station can deliver broadband Internet over a 40 square mile area.

The capacity of that wireless network is not bigger than any other wireless technology, which means that more base stations need to be added if a certain number of people are using the network--typically several hundreds to a 1,000 users.